The present invention relates to an apparatus for developing a magnetic field and, more particularly, to an apparatus which uses a permanent magnet for developing a magnetic biasing field in a magneto-optic disc system.
Conventionally, an apparatus for developing a magnetic biasing field to a memory medium by using a permanent magnet continues to produce a magnetic field on the memory medium for a long time even after the power source of a main body is switched off, because the permanent magnet is not fixed. Thereby, the permanent magnet continues to act on the memory medium.
However, in a magneto-optic disc system, when data is written or erased, a magnetic biasing field developed from outside is desired to be as low as possible except when the magnetic biasing field is necessary for actually writing or erasing data.
For example, if a magneto-optic disc is exposed to a high magnetic field for a great deal of time, there is the possibility that the signals recorded on the medium of the disc will deteriorated. This result is not desirable since of the magneto-optic disc will be reduced.